Visibility conditions are often poor when a vehicle driver is required to operate the vehicle's windshield wipers. Because of the typically poor visibility conditions when a vehicle's windshield wipers are being used, a vehicle's headlights should be turned on while the windshield wipers are being operated. To encourage this safe driving practice, many states have now enacted laws requiring that the headlights be turned on while a vehicle's windshield wipers are being operated.
There are numerous patents disclosing windshield wiper/headlight systems which turn a vehicle's headlights on in response to the operation of windshield wipers. U.S. Pat. No. 4,656,363 to Carter et al. is a representative patent which discloses a circuit for automatically operating the headlights in response to the operation of the windshield wipers. In addition, there are also patents which disclose systems that will place a vehicle's headlights in an "on" position in response to the closing of the windshield wiper switch and then maintain the vehicle's headlights in an "on" state independent of the operation of the windshield wipers. A system feature which maintains the headlights on independent of the operation of the windshield wipers prevents a driver from inadvertently turning off the headlights at night when the windshield wipers are turned off. U.S. Pat. No. 4,236,099 to Rosenblum and U.S. Pat. No. 4,956,562 to Benedict et al. disclose two different systems for maintaining the headlights on when the windshield wipers are turned off.
Prior art windshield wiper-headlight systems require complex circuitry to maintain the headlights on after the windshield wipers are turned off. Additional components and circuitry are also required to account for the polarity differences in windshield wiper systems of various types of vehicles. A simple and inexpensive windshield wiper/headlight system design is needed that will turn headlights on in response to the operation of the windshield wipers, and then maintain the headlights on once the windshield wipers are turned off. Such a headlight/windshield wiper system should be easily installed and retrofitted in cars, regardless of the polarity of the windshield wiper motor.